I really like the idea you've got here and though it was quite short, I think you've written in a very powerful manner. However, I feel that if you had just been a tad more descriptive about what you've already got here, it would really help the story. It would lend this beautiful sense of imagery that would work well.

I feel that you got Snape's tone right. This is how he talks to Harry- with an air of superiority, alright. But I didn't quite imagine him to even think like that because we find out about his true nature, his intentions and everything later on.

As for him calling Harry worthless, it's something he does all the time. But I'm just not entirely sure if he actually think that he is worthless :P

About his destiny, I'm sure it has a connection with Snape's conversation with Dumbledore where he remarks that it's as if they're merely preparing Harry like a pig for slaughter. There's some resentment there. I think you've got that bit right. Spot on :)

I think the idea is certainly unique and I haven't come across something like this despite the fact that I'm practically always reading fanfiction. Kudos for trying something new :) Good job, and I'm sorry if this is slightly harsh. Honestly, I did enjoy it. I just had a couple of pointers, that's all! :)